This disclosure relates to energy management, and more particularly to energy management of household consumer appliances. The disclosure finds particular application to cooking appliances and is particularly advantageously applied to such appliances with surface heating units and oven heating elements.
Currently utilities charge a flat rate, but with increasing cost of fuel prices and high energy usage at certain parts of the day, utilities have to buy more energy to supply customers during peak demand. Utility companies have to find ways to temporarily provide for this higher energy use, which comes at great expense to utility companies. Consequently, utilities are charging higher rates during peak demand. If the utility company can communicate that power is in high demand, home appliances, such as ranges that are typically used during peak time (later afternoon), could notify the consumer that demand is high and reduce peak power usage of the appliance and allow the utility company to shed load. This “demand response” capability in cooking appliances spread over thousands of customers would allow the utility company to shed a significant amount of peak load.
One solution that has been proposed is to provide a system where a control module “switches” the actual energy supply to the appliance or control unit on and off. However, there is no active control beyond the mere on/off switching.
Residential utility customers often have a plurality of electric surface elements for surface cooking and one or more ovens for baking and broiling. The surface elements and oven may be provided together in single appliance, for example a built-in or a free-standing range, or they may be provided separately in the form of a cooktop appliance and a wall oven. Typically, surface elements are used 2-3 times more often than the oven, and consume about the same peak power as the oven, but over half the amount of the time cycle. The best opportunity to shed power on surface elements is during high settings. At low settings, reducing power can result in undercooked food and since surface cooking is attended, the consumer can merely increase the power. High settings are typically initiated to perform non-direct-cooking related activities, such as boiling water. For normal cooking using surface elements, the element is set at settings on the order of 30% or less max power. However, for boiling, the maximum 100% power setting is used.
It is common during cooking for the oven and the surface elements to be used at the same time. During oven pre-heat, the oven operates at nearly 100% power. During this time, the surface elements may also operate at high power for functions such as boiling water. With the oven and the surface elements, on at the same time the cooking appliance may consume 6 kW or more of power.
While electronic surface unit controls can change or limit duty cycles in response to a “high demand”, many ranges use electromechanical power switching devices that are not electronic, for example infinite switches for controlling energization of the surface elements while using electronic controls for controlling energization of the oven bake and broil elements. This system aims to provide a way to reduce peak and average power with minimal changes to the design of currently produced cooking appliances with electromechanically controlled surface cooking elements, in a cost effective manner. By implementing a simple control, this system is able to react to either a discrete normal demand or higher demand signal. Therefore, this system provides a simple, low cost method to shed both peak and average power that does not require relatively expensive and complex all electronic appliance control systems. It is proposed for the surface elements and the oven to share power and still perforin their intended functions by operating the oven at full power when no energy is being used by surface heating elements, and operating the oven at a reduced power level when energy is being used by the surface heating elements. This reduces the peak and average power consumed by the appliance. This system may be installed on existing products without adding expensive electronic surface control devices that require extensive system level software developments, safety critical hardware & and software interactions, etc.